The present invention relates generally to seals, and more particularly to a mechanical end face seal which is adapted to use in extremely severe working environments.
Some years ago, improvements were made in end face seals, with the result that, for many applications, seals would quite literally last the entire lifetime of the sealed mechanism. In order words, the sealed part, or other parts associated with it, would wear out before the seal itself would require replacement. Prior to that date, sealed mechanisms exposed to severe environments required expensive seal replacement, in turn causing inconvenience and expensive "down time," the use of replacement parts and labor, etc. A seal of the type which was an effective "lifetime" seal is shown in U.S. Pat. No. 3,241,843. Since that time, some improvements have been made in these mechanisms, but the basic design is sound and has proved very successful.
As is often the case, however, even excellent products are capable of further improvement, and even very rugged products are sometimes placed in environments which are so severe that they do not have the anticipated life they would have in less severe circumstances.
The present invention relates to a seal which is intended for use with rock drills, to act as a drill bit seal so as to exclude grit from a sealed region while retaining lubricant therein. Rock drills, by their nature, are exposed to abrasive grit, and, moreover, are subjected to severe vibration over a wide range of frequencies. Seals of this type may also sometimes encounter abrasive materials as well as clays and the like which may be strongly acidic or alkaline.
Prior seal designs used in rock drill and like environments have not been particularly successful. These seals lacked the ability to seal under conditions of severe impact and vibration.
A typical seal of the present invention is exposed to the epitome of severe conditions. A preferred application for this seal is in rock crusher drills of the so-called "raise bore" type. These rock crusher/drilling machines used in "raise boring" operations are well known to those skilled in the art. They generally include a gigantic main frame which is rotated by an extremely powerful motor about the axis of a fixed shaft. This frame in turn contains a large number of rock bit carriers, each of a clevis or bifurcated form. These elements on the carrier locate the two ends of a fixed spindle or shaft which extends centrally through a bit. The bit itself resembles a large tapered roller bearing, containing on its outer surface a plurality of rows of individual, very hard spikes, customarily made from tungsten carbide or the like. In use, the frame is rotated, moving with it the carriers affixed thereto; the drill bits mounted on the carriers spin about the axis of the spindle or the like by reason of being journalled on bearings, and permit the drill bit to apply a crushing force to the rock or other surface disposed about it. The expression "raise boring" derives from the fact that, in use, the frame is moved upwardly to drill a vertical bore from an existing mine shaft to another mine shaft lying on a higher level, or to drill to and through the surface of the earth for purposes of ventilation, excavation or the like.
The seals just described preferably use specialty rubbers such as fluoroelastomers or the like in a novel configuration, in combination with primary seal rings and auxiliary springs and retainers for use in severe environments.
Previous seals intended for this purpose having lacked one or more advantages or characteristics desirable in these applications, it is an object of the present invention to provide an improved composite end face seal for use in severe service environments.
Another object is to provide a seal with a pair of identical elements, arranged in mirror image form and adapted in use to cooperate to provide a rugged and reliable end face seal.
Another object is to provide a seal having an annular secondary seal member with a pair of axial flanges joined to each other by a contoured web of a particular cross-section.
Still another object is to provide a seal having primary rings of generally L-shaped cross-section, with radial flanges being ground or otherwise finished so as to provide an effective abutting primary end face seal.
A further object is to provide a seal unit having opposed primary rings urged axially into primary sealing engagement by wave-type springs which act directly on the seal rings.
A still further object is to provide a secondary seal unit or a seal assembly, which secondary unit provides a secondary seal and also locates the primary rings with respect to the counterbore and which may or may not contribute to the seal end face load.
Yet another object is to provide a novel end face seal which can be pre-assembled or unitized for shipment and installation so as to reduce cost and improve reliability.
A still further object is to provide a seal which withstands vibration and operates successfully in a highly abrasive environment.
A still further object of the invention is to provide a so-called mirror image, three-piece seal which consists of right and left hand seal pairs, each made from identical springs, primary rings, and secondary members, unitized by a pair of seal carriers.
Yet another object is to provide a seal unit which will be effective under a wide range of axial movement, and which will be effective to seal the lubricated cavity without excessive force application which might cause premature wear.
Still another object of the invention is to provide a seal which includes or is adapted to include its own housing unit which is compatible with a drill bit carrier or drive shaft assembly so that the seal and its carrier may be manufactured to close tolerances at the factory, shipped as an assembly, and installed without destructive or damaging disassembly and reassembly.
A further object of the invention is to provide a cartridge or unitized seal assembly which includes pairs of primary and secondary seal rings with auxiliary springs and clamp rings, with one-half of the symmetrical or mirror image seal being carried in a unitizing casing of stamped or drawn material with the other portion being carried by or received in a machined seal ring carrier.
A still further object of the invention is to provide a unitized type seal which may be installed reliably, that is, which, when installed, will in effect advise the operator that the installation is complete and correct.
A still further object of the invention is to provide a seal cartridge which includes a pair of carrier units for two preassembled seal halves, one carrier unit having surfaces adapted to engage a counterbore to a predetermined depth or installed "height" with the other carrier being a machined assembly adapted to be positioned by a snap ring or the like and held against rotation by drive pins or the like.
Another object of the invention is to provide a unitized seal arrangement which may be installed in place as a simple operation at the same time a drilling bit or the like is installed, and which permits removal and replacement of the seal without requiring removal or replacement of other rotary sealed parts.
The foregoing and other objects and advantages of the invention are achieved in practice by providing a seal unit comprising a pair of assemblies, each have three substantially identical components including a wave type spring element, a primary seal ring of generally L-shaped cross-section and having radial and axial flanges, with one radial flange having an end face seal band surface thereon and an opposite surface as well as a radially outer axial surface being adapted to receive a secondary ring, and a secondary seal ring made from an elastomer, being of annular form and having a generally U-shaped cross-section.
The invention is also carried into practice by providing a cartridge-type seal which includes a pair of cooperating seal carriers having means permitting them to be locked together or preassembled and lubricated, and which is designed to permit ready installation with associated sealed parts at the work site, with one carrier being a drawn or stamped carrier and the other being machined carrier and the carriers having cooperative locking or unitizing mean thereon which prevent unattentional disassembly but which permit the seal to operate through an intended range of install tolerances or "working heights" during operations.
The exact manner in which these and other objects and advantages of the invention are carried into practice will become more clearly apparent when reference is made to the accompanying detailed description the preferred embodiments set forth by way of example, and to the accompanying drawings wherein like reference numerals indicate corresponding parts throughout.